The present invention relates generally to vehicles, and more specifically to a method and apparatus for generating lift for a vehicle.
Vertical take-off and landing (VTOL) technology often uses diverted exhaust gases from a gas turbine engine to distribute lift along an aircraft. VTOL is typically used with engines that do not generate a bypass air flow or that operate with a generally low bypass ratio because of the higher-energy exhaust gases they produce However, such higher-energy engines often have a lower fuel efficiency than engines having a greater bypass ratio. Accordingly, some aircraft having VTOL suffer from a high specific fuel consumption during cruise portions of flight. Additionally, some known VTOL systems use a lift fan driven by a shaft coupled to a turbine within the engine. The turbine and shaft may disrupt the exhaust flowfield within the engine and thereby reduce the fuel efficiency of the engine, especially during cruise portions of a flight. Furthermore, the gas exiting some known VTOL systems to generate lift may have a temperature greater than about 800° F. Such high temperatures may cause damage to surfaces from which the aircraft takeoffs and on which the aircraft lands, such as runways, aircraft carrier decks, and/or natural terrain. For example, temperatures above about 800° F. may cause brush fires when an aircraft takes off from and/or lands on natural terrain.